The Claus process essentially involves the catalytic conversion of hydrogen sulphide to sulphur and water. The process is widely used to eliminate sulphur compounds from gas streams as a pollution control measure At the same time, the process is commercially attractive because it results in the production of a saleable sulphur product. A primary use of the Claus process is to remove hydrogen sulphide from acid gas streams that result from oil refining processes. In this application, hydrogen sulphide is oxidized to sulphur dioxide and the hydrogen sulphide and sulphur dioxide react to produce elemental sulphur and water. The process is carried out at high temperature in a catalytic converter containing activated alumina catalyst.
It has been recognized that, if the Claus process is carried out at temperatures below the dewpoint of the sulphur that is produced (e.g. about 230.degree. C. to 116.degree. C.), conversion to sulphur increases substantially. However, as the reaction proceeds and sulphur is adsorbed into the catalyst in the converter, the effectiveness of the catalyst is reduced and the catalyst must be periodically regenerated. A second catalytic converter is therefore provided so that the catalyst in one converter can be regenerated while the other is operated at the dewpoint for sulphur recovery. Regeneration can take place "on-line" by directing into the converter the full forward flow of the gas stream, which is at high temperature. This causes the sulphur that was previously condensed on the catalyst to be vapourized. The vapourized sulphur is recovered downstream in a separate condenser.
An enhancement to this process involves the provision of three catalytic converters instead of two. In this process one catalytic converter is in regeneration and two converters are operated below the dewpoint. Again, regeneration takes place by directing into the relevant converter the full forward flow of the gas stream, which is at high temperature. The addition of the extra converter operating below the dewpoint provides overall higher levels of sulphur recovery.